The invention relates to an apparatus for the continuous drying of finely divided solids by evaporating the moisture adhering thereto.
Apparatus of the kind specified are disclosed in Swiss Patent No. 343,887. They have a vertical drying chamber between an inner tube and an outer tube. A connection for feeding moist solids leads into the upper end of the drying chamber, at whose bottom end there is provided a hopper for the discharge of dried solids. The outer tube is surrounded by a heating jacket through which a heat medium flows and directly heats the wall of the outer tube. By heating the outer tube wall, heat is supplied continuously to the moist solid during the drying process. The dried solids are caught in a container. Preheated clean gas fed into the moist solids to suspend them escapes through the inner tube. Separation of the dried solid from the gas is performed in a centrifugal air separator.
DE-PS No. 1 085 751 discloses an apparatus for drying wheat, in which the wheat to be dried is sprinkled onto surfaces inclined from the horizontal and disposed one following the other, and is thus exposed to the action of infrared radiators.
In the drying of finely divided solids which become thermal insulators as they are dried, considerable problems are involved in thermal transfer, because, as long as their content of adherent moisture is still high, such solids can be dried well, but as the dryness increases their thermal insulating properties become increasingly apparent, until the drying process finally comes to a halt.